The American Civil Liberties Union and the National Rifle Association agree about very little. They are often on opposite sides in major cases, and they certainly have starkly different views about gun rights.
But when the Supreme Court agreed to hear the N.R.A.’s free-speech challenge to what it said were a New York official’s efforts to blacklist it, one of its lawyers had a bold idea. Why not ask the A.C.L.U. to represent it before the justices?
“The N.R.A. might be thought of as the 800-pound gorilla on the Second Amendment,” said the lawyer, William A. Brewer III. “Clearly, the A.C.L.U. is the 800-pound gorilla on the First Amendment.”
David Cole, the civil liberties group’s national legal director, said the request in one sense posed a hard question.
“It’s never easy to defend those with whom you disagree,” he said. “But the A.C.L.U. has long stood for the proposition that we may disagree with what you say but will defend to the death your right to say it.”
Mr. Cole’s group has been subject to occasional criticism that it has become less attentive to free-speech principles and more devoted to values rooted in equality in recent years. He rejected that critique, even as he acknowledged that the decision to represent the N.R.A. would not meet with universal praise.
“It will be controversial, within and outside the A.C.L.U.,” Mr. Cole said. “But if it was easy, it wouldn’t mean as much.”
He added: “In this hyper-polarized environment, where few are willing to cross the aisle on anything, the fact that the A.C.L.U. is defending the N.R.A. here only underscores the importance of the free speech principle at stake.”
In a statement, the civil liberties group drew a distinction.
“The A.C.L.U. does not support the N.R.A. or its mission,” the statement said. “We signed on as co-counsel because public officials shouldn’t be allowed to abuse the powers of the office to blacklist an organization just because they oppose an organization’s political views.”
A central question in the case, National Rifle Association v. Vullo, No. 22-842, is whether Maria Vullo, a former superintendent of the New York State Department of Financial Services, leveraged government power in a way that violated the First Amendment.
According to the N.R.A.’s lawsuit, Ms. Vullo crossed a constitutional line by encouraging banks and insurance companies to stop doing business with the group after the 2018 school shooting in Parkland, Fla. The rampage left 17 people dead.
A unanimous three-judge panel of the U.S. Court of Appeals for the Second Circuit, in New York, ruled against the N.R.A. Judge Denny Chin, writing for the panel, acknowledged that government officials may not “use their regulatory powers to coerce individuals or entities into refraining from protected speech.”
“At the same time, however,” he wrote, “government officials have a right — indeed, a duty — to address issues of public concern.”
Ms. Vullo’s actions were on the right side of the constitutional line, Judge Chin wrote. Key documents, he said, “were written in an evenhanded, nonthreatening tone and employed words intended to persuade rather than intimidate.”
The question of when government advocacy violates the First Amendment is before the justices in another case this term. That one concerns the Biden administration’s efforts to persuade social media companies to delete what the government said is misinformation about topics like the coronavirus pandemic and the 2020 election.
In its petition seeking Supreme Court review, the N.R.A., represented by Mr. Brewer’s firm and Eugene Volokh, a prominent First Amendment scholar, said the appeals court’s ruling could have sweeping consequences.
“The Second Circuit’s opinion below gives state officials free rein to financially blacklist their political opponents — from gun-rights groups to abortion-rights groups to environmentalist groups and beyond,” the petition said.
In response, lawyers for Ms. Vullo wrote that “the ability to opine on important questions of public policy is vital to the work of many government officials.”
The brief added that Ms. Vullo “did not violate the First Amendment by expressing her views regarding a national tragedy and encouraging regulated entities to consider their relationships with gun-promotion organizations.”
Neal K. Katyal, a lawyer for Ms. Vullo, declined to comment on the A.C.L.U.’s entry into the case.
Mr. Cole, who will argue for the N.R.A. when the case is heard by the justices, probably in March, said it concerned principles that apply to all kinds of groups.
“If Maria Vullo can do this to the N.R.A., then why couldn’t a regulator in Texas do it to an immigrants’ rights group or a regulator in Arkansas do it to Planned Parenthood?” he asked.
He added that federal officials could also abuse their power under the appeals court’s ruling. “Donald Trump has made no bones about his desire to retaliate against his opponents,” Mr. Cole said. “This would be a playbook for him to do exactly that.”